Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2002-06-05
2004-11-02
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S474000, C524S490000, C585S010000, C106S502000
Reexamination Certificate
active
06812274
ABSTRACT:
The present invention relates to pigment concentrates comprising at least one pigment, a polyethylene wax prepared from ethylene and, if desired, one or more olefins using a metallocene catalyst, if desired a thermoplastic polymer and, if desired, additives.
Numerous pigments are marketed in the form of a pigment concentrate since this makes processing easier when coloring plastics. These formulations generally comprise, in addition to the pigment, a dispersant, for example a wax, and, if desired, a thermoplastic polymer, usually a polyolefin. The thermoplastic polymer is also referred to as a carrier polymer. The wax serves to disperse the pigment finely in the formulation and to stabilize this dispersion. A typical commercial formulation of such a pigment concentrate (masterbatch) comprises 25% by weight of pigment, 10% by weight of wax and 65% by weight of a polyethylene. The wax used is frequently a polyethylene wax which can be obtained, for example, by free-radical polymerization or by Ziegler-Natta catalysis. The polyethylene wax can be modified so as to make it polar, for example by oxidation. The ratios of the individual components can be varied within certain limits.
A critical prerequisite for the usability of such a pigment concentrate is the correct choice of the wax component. Although it is not colored itself, it influences the brilliance of the pigment concentrate. For more detailed information, reference may be made, for example, to the product brochure “Luwaxe®—Anwendung in Pigmentkonzentraten” about polyethylene waxes from BASF AG.
The pigment agglomerates have to be wetted well by the wax to prevent clumping together of the agglomerates. A small number of relatively large pigment agglomerates makes less contribution to the pigmenting power of the pigment concerned than does a larger number of smaller pigment agglomerates.
It is therefore an objective to allow no large pigment agglomerates to be formed during the formulation process. Furthermore, it is desirable to separate any previously formed agglomerated pigments and to split them up into their primary particles. Finally, the primary particles should also remain separated after the formulation process and not reagglomerate during cooling.
To achieve this, the wax has to meet a number of requirements. One of these requirements concerns the viscosity of the melt. The viscosity of the melt should be as low as possible so that the molten wax can readily penetrate the voids within the agglomerates of the pigment during formulation, which is usually carried out by mixing at a temperature above the melting point of the wax. As a result of the shear forces applied in this way, the agglomerates are more readily split up into the primary particles.
The wetting capability of the waxes should also be good.
Polar groups can in principle be introduced into a wax by means of various process steps.
One method is to partially degrade the wax by means of atmospheric oxygen or peroxide compounds. Examples of peroxide compounds which can be used are hydrogen peroxide (H
2
O
2
) and dialkyl peroxides. Partial degradation methods introduce hydroxyl groups and carboxyl groups as polar groups into the macromolecules. These polar groups are distributed nonuniformly over the molecule, as a result of which the wetting capability of the molecule chains of the waxes is not optimum.
Another method is to use polar comonomers such as acrylic acid, methacrylic acid, acrylic esters, methacrylic esters or vinyl acetate, which may be suponified. A disadvantage of this process is that polar comonomers can act as catalyst poisons for Ziegler-Natta catalysts and the catalysts therefore lose activity. A further disadvantage is that the comonomers are not incorporated uniformly into the waxes. Comonomers are usually incorporated preferentially into the short-chain molecules, which leads to undesirably nonuniform properties of the wax.
It has been found that many pigment concentrates have insufficient brilliance for high-quality applications. This problem can be solved only to a limited extent by a larger proportion of pigment. The price of the pigment is the decisive factor for determining the production cost of a pigment concentrate. For this reason, a higher proportion of pigment would-be an economic disadvantage.
Conversely, it can also be desirable to have an equivalent pigment concentrate containing lower proportions of the expensive pigment for less demanding applications.
EP-A 0 890 584 discloses the use of metallocene polypropylene waxes having an isotacticity index greater than 70% for masterbatches. However, a disadvantage of using a metallocene polypropylene wax is that specific racemic isomers of the metallocenes are necessary for preparing isotactic polypropylene. The meso isomer formed in customary syntheses firstly has to be separated off and then has to be either discarded or converted into the desired racemate in a further step.
Finally, it has been found that the brilliance of the masterbatches does not continue to increase significantly at high pigment concentrations, which is attributable to unsatisfactory dispersion. Poorly dispersed agglomerates can be detected, for example, by microscopic examination.
It is an object of the invention
to provide pigment concentrates which make it possible to color plastic moldings and plastic sheets and which are easy to prepare and have improved brilliance compared to the prior art without the percentage of pigments having to be increased,
to provide a process for producing these concentrates,
to produce plastic moldings and plastic sheets which are colored by means of the pigment concentrates of the present invention, and
to find a process for coloring thermoplastic polymers and moldings by means of the concentrates of present invention.
We have found that this object is achieved by using metallocene polyethylene waxes as dispersants in pigment concentrates. We have found that these give better results than conventional polyethylene waxes.
The present invention provides pigment concentrates (masterbatches) comprising the following components:
at least one pigment selected from among inorganic or organic pigments.
Examples of inorganic pigments are
zinc white, zinc sulfide, lithopone, lead white, lead sulfate, chalk, titanium dioxide;
iron oxide yellow, cadmium yellow, nickel-titanium yellow, chromium titanium yellow, chromium yellow, lead chromate, bismuth vanadate, Naples yellow or zinc yellow;
ultramarine blue, cobalt blue, manganese blue, iron blue;
ultramarine green, cobalt green, chromium oxide (chromium oxide green);
ultramarine violet, cobalt violet, manganese violet;
ultramarine red, molybdate red, chromium red, cadmium red;
iron oxide brown, chromium-iron brown, zinc-iron brown, manganese titanium brown;
iron oxide black, iron-manganese black, spinel black, carbon black;
orange-colored spinels and aluminas, cadmium orange, chromium orange, lead molybdate;
aluminum or Cu/Zn alloy.
Examples of organic pigments are
metal phthalocyanines such as phthalocyanine blue or phthalocyanine green, also perylene red, diaryl yellow, isoindoline yellow, quinophthalone pigments, quinacridone pigments, benzimidazolone pigments, malachite green, thioindigo, monoazo pigments, diazo pigments, coated azo pigments, naphthol AS pigments, benzimidazolone pigments, diketopyrrolopyrroles, indanthrone, azo condensation pigments, diazo condensation pigments, anthraquinone pigments, pyrazolones, perinones, aminoketone pigments, indigo or triphenylmethane pigments.
Overviews of customary inorganic and organic pigments may be found, for example, in K. Leissler and G. Rösch, Kunststoffe 1996, 86, 965 and in
Ullmann's Enyclopädie der technischen Chemie
, 4th Edition, keywords: pigments: introduction; Vol. 18, p. 547 ff., Organische Pigmente, Vol. 18, p. 661 ff; Thieme Verlag Stuttgart, 1977. It is possible to produce concentrates comprising one pigment or mixtures comprising two, three or more diffetent pigments.
Polyethylene wax, which is a wax-like molding composition comprising polyethylene or copolym
Deckers Andreas
von Koenig Naria Edlu Keene
Weber Wilhelm
Weiss Stefan
BASF - Aktiengesellschaft
Keil & Weinkauf
Lee Rip A.
Wu David W.
LandOfFree
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